Case of pronouns after than

Q:

How do I decide which pronoun to use after than—for
example, than I or than me?

Anonymous
New Jersey

A:

Surprisingly, you will find that than me is more often
correct, or at least more often used, than than I.
Than I is correct and is heard if a verb follows
I (or any subject), in forms such as than I am,
than I do, than I have, than
you want, than Bob expects, etc. But, as
Marilyn found in her corpus research, than I without
a verb following does not appear to be heard very often.

When you use a pronoun after than, you can complete the sentence in
your mind, although it is not necessary to speak the whole sentence.

(a) Howard cooks better than I.

(b) Howard cooks better than I cook.

(c) Howard cooks better than I do.

You can continue sentence (a), and then it’s clear that you need
to use I as the subject of the next verb, which will
be either cook or the auxiliary do.
Sentences (a), (b), and (c) all have the same meaning. (a) would not
appear very frequently, except in hypercorrect usage, but (b) would
sometimes, and (c) would appear very frequently.

Informally, with the same meaning, you can say better than
me—as in sentence (d), below—although strict grammarians
might object to this construction:

(d) Howard cooks better than me.

Sentences (a), (b), (c), and (d) all have the same meaning, then. To
avoid problems—if you think you seem either too erudite using
I or too unschooled using me—use a complete sentence, which would
be (b) or (c) above. (c) would be the most usual and conversational
construction.

It’s not difficult to select the proper pronoun when it’s
clear that you are expressing the subject of the second clause,
as in the sentence above about my cooking in relation to Howard’s
cooking.

Things are not always so clear, however. What about expressing the
object of the verb of the second clause (like)?

John likes Mary more than he likes …?

John likes Mary more than me [or I]?

The real problem is caused by reducing a clause to a phrase. Consider
these examples contributed by Barbara Matthies:

Subject of like, the verb in the second clause (I):

(e) John likes Mary more than I like her.

This can be reduced to:

(f) John likes Mary more than I (do).

Object of like, the verb in the second clause (me):

(g) John likes Mary more than he likes me.

The reduced form:

(h) John likes Mary more than me.

Compare the reduced examples (f) and (h); then you will see the source
of the problem. Example (f) requires the subject pronoun I,
but (h) requires the object pronoun me because different parts
of the clause have been reduced. Sentences (e) and (f) have different
meanings from (g) and (h).

In the sentences above, (e), (f), (g), and (h) are all correct. Sentence
(e) is clear, sentence (f) needs the do in order to
be clear. Sentence (g) is clear, but sentence (h) might be unclear in
some contexts, and instead, (g) should be used if me
is to refer to the object of the verb like.